help about dual core in windows

hello! i have built a dual core system amd x2 3800+ and it is activated in the bios as dual core...will it be automatically activated in windows xp? or do i have to install like special drivers so if a multithreaded program came along will it work automatically or do i need to set a setting somewhere? thanks?

Another thing you can do is when you get to windows, for the most CPU demanding applications, press ctrl+alt+delete and go to task manager, then go to processes and set affinity to core 0 and core 1 to distribute the world load.

That works wonders when I am gaming and using something else in the background..